This invention relates generally to the field of data storage devices, and more particularly but not by way of limitation to an apparatus and associated method for fixing a data storage disc in balanced rotation with a drive motor.
Modern data storage devices such as disc drives are commonly used in a multitude of computer environments to store large amounts of data in a form that is readily available to a user. Generally, a disc drive has a disc stack assembly with one or more data storage discs that are rotated by a motor at high speeds. A clamp is used to fix the discs in rotation with the motor. Each disc has a data storage surface divided into a series of generally concentric data tracks where data is stored in the form of magnetic flux transitions.
A data transfer member such as a magnetic transducer is moved by an actuator to selected positions adjacent the data storage surface to sense the magnetic flux transitions in reading data from the disc, and to transmit electrical signals to induce the magnetic flux transitions in writing data to the disc. The active elements of the data transfer member are supported by suspension structures extending from the actuator. The active elements are maintained a small distance away from the data storage surface as the data transfer member flies upon an air bearing generated by air currents caused by the spinning discs.
A continuing trend in the industry is toward ever-increasing the data storage capacity and the processing speed while maintaining or reducing the physical size of the disc drive. Consequently, the data transfer member and the discs are continually being miniaturized, data storage densities are continually being increased, data storage disc speed is continually being increased, and data transfer member fly heights are continually being decreased. One result is an overall increased sensitivity to vibration.
One source of vibration comes from an out-of-balance condition of the disc stack assembly. This can cause positioning errors making the transfer of data from and to the disc unreliable. If the vibration induces too much displacement to the disc or the data transfer member then head crashes can occur, likely causing damage to the data transfer member rendering the data storage device unusable.
One balancing solution known in the art is to bias alternating discs in opposite directions against the centrally supporting motor hub so as to distribute the total disc mass substantially equally around the motor axis of rotation. Although used primarily for multi-disc stacks, this solution has also been suggested in single-disc stacks by biasing a spacer member and the disc. A disadvantage is the additional product cost of the spacer and the process complexity associated with the biasing procedures.
Another group of solutions can be categorized generally as those that add or remove an amount of mass to/from the disc stack to compensate for an observed unbalanced condition from balance testing. In some cases the compensation occurs after the clamp has been attached, such as by attaching a clip or an epoxy material to add balancing weight. Alternatively, the disc stack can be balance tested without the clamp and eccentric spacers can be added to provide the balance weight as needed.
In all these solutions, however, there remains a need for improving the manner of positioning and attaching the clamp in order to preserve the observed balance conditions during balance testing. The imbalance caused by any eccentricity of the clamp relative to the axis of rotation could be assumed negligible in the recent past. However, modern demands for reduced vibration thresholds make the clamp placement a significant factor. Also, high speed automated assembly methods used today demand robust methodologies for attaching the clamp so as to be registered with the axis of rotation.
In some approaches the clamp has a central opening that receivingly engages the outer diameter of the motor hub. If the central opening is sized in a closely-fitting mating relationship with the hub then the clamp can be precisely located. However, any scraping action of the clamp against the hub can result in harmful particulates that interfere with effective disc drive operation. Contrarily, if the central opening is sized for clearance with the hub then the clamp must be precisely positioned before attachment.
Other approaches recognize the benefits of attaching the clamp with a single fastener attached to the rotating hub. These approaches depend on precise placement of the clamp to the hub, and require an oversized clearance aperture through which the fastener is passed and joined to the hub in attaching the clamp.
It has been determined that an improved single-screw disc fixing apparatus is possible wherein the clamp member is provided with a reference surface associated with the clamp axis of rotation, and a fastener member is provided with a registration surface that is matingly engageable with the reference surface. Accordingly, the fastener member can be used to register the clamp relative to a longitudinal axis of the fastener. The fastener can then be attached to the hub so as to register the clamp to the motor axis of rotation. It is to these improvements and others as exemplified by the description and appended claims that embodiments of the present invention are directed.
Embodiments of the present invention are directed to a disc fixing apparatus for fixing a data storage disc in rotation with the hub of a motor that is rotatable around a motor axis of rotation in a data storage device. The disc fixing apparatus comprises a clamp engageable with the hub comprising a reference surface associated with the clamp axis of rotation. The disc fixing apparatus further comprises a fastener comprising a registration feature cooperable with the reference surface. The fastener is attachable to the motor hub fixing the disc and hub in rotation and registering the clamp to the motor axis of rotation.
In one embodiment of the apparatus the clamp is adapted for coaxial registration to the longitudinal axis of the fastener, and in turn, is adapted for coaxial registration to the motor axis of rotation. The clamp can comprise an annular contact surface pressingly engageable against the disc and concentric with the clamp axis of rotation.
Embodiments of the apparatus contemplate the reference surface defining an opening receivingly engageable with the registration feature in a closely fitting relationship, such as a frictional-fitting relationship so as to maintain the clamp registration with the fastener.
Embodiments of the apparatus further contemplate the registration feature comprising a surface disposed parallel to the fastener longitudinal axis, such as a cylindrical registration feature for use with a reference surface defining a circular opening. The reference surface can be characteristically arcuate and thereby receivingly engageable with the registration feature in a point contact relationship. Furthermore, the registration feature can terminate in an arcuate surface operably engageable with the reference surface in a mating relationship.
Embodiments of the apparatus further contemplate a rough alignment feature comprising an opening defined by the clamp receivingly engageable with a removable locating member that is passable through the clamp and engageable with the hub to fix the clamp and hub in rotation.
Embodiments of the apparatus further contemplate a balancing weight added to the clamp or a balancing weight removed from the clamp, such as a relief notch, characteristically positioned and sized to operably compensate for rotational imbalance.
In another aspect of the embodiments of the present invention a disc stack assembly is provided comprising a motor comprising a hub rotatable around a motor axis of rotation with a disc disposed around the hub. A disc fixing apparatus is provided comprising the clamp reference surface and fastener registration feature fixing the disc and hub in rotation and registering the clamp with the motor axis of rotation.
In yet another aspect of the embodiments of the present invention a method is provided for fixing a disc in balanced rotation with a rotatable hub of a motor around a motor axis of rotation. The method comprises: providing a clamp member comprising a reference surface associated with a clamp axis of rotation; registering the clamp member with a longitudinal axis of a fastener; aligning the fastener and clamp together with the hub; and attaching the fastener to the hub so as to register the clamp member with the motor axis of rotation.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.